Last week, the Metropolitan Police confirmed they had found a small bottle believed to be the source of the contamination.
Matthew, from Warminster, Wilts, said his brother recalled that Dawn had sprayed the perfume on both of her wrists.
In March, the Wiltshire cathedral city was the scene of the novichok poisoning of former Russian spy Sergei Skripal and his daughter Yulia, who both survived.
Ms Sturgess fell ill on the morning of June 30 and died eight days later in Salisbury District Hospital, while Mr Rowley was left fighting for his life after also becoming contaminated. Sturgess died on July 8 and counter-terror detectives have launched a murder probe.
PA said investigators believe Sturgess was exposed to at least 10 times the amount of nerve agent as the Skripals came into contact with.
"In the past four and a half months, our hospital has treated all five victims while the world looked on and yet we have never closed our doors to the public".
A source who has been briefed on the progress of the investigation said: "They want to get out of Charlie the best account of where he was and what happened so they can get to the bottom of this matter".More news: Trump backs down, says he misspoke on Russia meddling
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'I tried to console him and said that he needed to try and keep as strong as possible so he can recover.
PHE medical director Paul Cosford reiterated its previous advice: "Do not pick up any items such as syringes, needles, cosmetics or similar objects made of materials such as metal, plastic or glass".
Health officials on July 20 said 45-year-old Charlie Rowley "is well enough" to be discharged from Salisbury District Hospital and that his release into the public "creates no risk to anyone in the community".
A Scotland Yard spokesman said: 'The investigation into the Salisbury attack remains ongoing and we're not prepared to discuss any lines of enquiry at this stage'.
The New York Times previously reported that British investigators believed the father and daughter were likely poisoned by current or former agents of Russia's military intelligence service, known as the GRU.
Britain and its allies blamed Russia for the attack in March on the Skripals, prompting the biggest Western expulsion of Russian diplomats since the Cold War.
Authorities are looking whether the couple's nerve agent exposure was linked to a recent attack on Skripal and Yulia.